Sheave device for derricks



g 1939- J. w. wuNscl-l' SHEAVE DEVICE FOR DERRICKS Filed Feb. 16, 1937 Patented Aug. 8, 1939 UNITED STTES TENT orrics 1 Claim.

My invention relates to a sheave device and it is more especially applicable to collapsible tripod derricks commonly used on motor trucks and tractors for pole setting and other opera- 5 tions, and it is also adapted to be applied to stiff leg derricks and derricks of the type in which the head sheave is usually mounted in a rigid position. In various derricks of the above character, in which the sheave is rigidly mounted, when the pull on the rope or cable is not in a direct line below and in the plane of the sheave, but more or less at one side of it, the rope or cable will necessarily drag on the side plates of the sheave and cause friction and wear of the rope or cable as well as the sheave and side plates of the sheave housing.

The object of the present invention is to provide a sheave which is pivotally mounted, preferably on an extension from one of the derrick legs,

i. e., the center leg, so that the sheave can oscillate on its pivot. Preferably, the sheave is so mounted that it oscillates on an axis which coincides with the rope or cable which lies tangent to the upper side of the sheave so that as the s sheave rocks sidewise the rope or cable extending downwardly from the sheave to the load will not be subject to the excessive friction referred to above, and at the same time the sheave can rock laterally without causing a lifting of the load by reason of the rocking motion of the sheave or, in other words, the sheave may rock freely to take a position according to the location of the load in regard to the plane of the sheave.

If the load is not in the same vertical plane as the sheave the sheave may rock. and this will also avoid the tendency of the rope to run off the sheave.

The present device is simple, inexpensive and rigid and durable in construction. Further details and objects of my invention will be set forth in the following detailed description thereof.

In the drawing forming part of this application, Figure l is a side elevation showing the. apex of a derrick with my invention applied thereto, Figure 2 is an end elevation thereof, and

Figure 3 is a longitudinal, sectional view taken on the line 3-3 of Figure 2.

While I have shown in. the drawing an embodiment of my invention applied to a tripod derrick, only so much of the derrick being shown as is essential to an understanding of the invention, the invention is applicable to any special or standard type of derrick. In the drawing I have shown members connected to the side legs of the derrick pivotally connected to the angle or intermediate portion 5 of a bracket substantially of right angle form by a stud or bolt 3. One angle member l of the bracket, which may be of cylindrical form as shown, is adapted for the connection of one end of a leg 2 on the derrick and 55 shown as fitted into the tubular end of the middle leg 2 of the derrick. The other angle member 6 of the bracket is provided with a tubular bore 1 the axis of which extends in the direction of the angle member 4 of the bracket. The angle por- 10 tion 5 of the bracket is substantially flat at the portion through which the stud 3 is extended and the connecting members. for the derrick legs I are pivotally mounted on the opposite ends of said stud to connect the legs I to the leg 2 of 15 the derrick. A sheave supporting frame is supported by the bracket member 6 to rotate about the axis of the bore therein and comprises a bifurcated member including a pair of plates 8 connected at an edge portion in parallel and 20 spaced relation with bolts 9 extended through openings at the outer or forward corners of the plates as indicated in Figures 1 and 3, the plates beingadapted to enclose and house a sheave ID, the latter being mounted to revolve between the .25 plates on an axle ll which is mounted in open ings in alined hubs l2 preferably formed integral with the plates 8. The plates 8 at the left hand end and adjacent the upper portion thereof, as viewed in Figures 1 and 3, are arranged with an 30 integral connecting portion I3 having a projection l4 extended laterally therefrom opposite the plates with an opening therethrough, said projections being engaged in the bore 1 of the angle member 6 with the portion l3 abutting the 35 end of said angle member whereby the sheave carrying frame may be revolved in the bore of said angle member of the bracket, the tubular portion Id of the sheave carrying frame being held in the bore l against outward movement by 40 a collar l6 engaged on the tubular portion l4 extended from the end of the angle member 6 of the bracket and secured thereon by a locking set screw ll.

The opening H3 in the projecting portion. I4 is 45 extended through the portion l3 and may be of circular form, or may be in the form of a slot I!) which is preferably elongated in the vertical direction; and the upper run 20 of the rope or cable passing substantially axially through the 5 bore 18 and the slot l9 to engage in a peripheral groove 2| substantially in a plane tangential to said run of the cable or rope and extending partly around the sheave Ill, sothat this rope or cable is directed at a tangent to the sheave when not sagging or when a. load is being carried by the rope or cable. The axis on which the sheave housing oscillates is the center line of the rope or cable 20 in the preferred form of my invention because the axis of the shaft I4 coincides with the axis of the upper run 20 of the rope or cable. After the rope or cable passes partly around the sheave l0, lying in the groove thereof, and lying between the plates 8 of the sheave housing, the cable extends downwardly as shown at 22 in a vertical or approximately vertical direction.

When a load is applied to the vertical run 22 of the rope or cable, if the center of gravity of the load is not directly in the plane of the sheave, that is to say, if the center of gravity of the load is on either side of the normal plane of the sheave, then when the rope or cable is drawn to lift the load there will be no undue friction of the rope or cable against the sheave or the side plates 8 because of the sheave, instead of being rigid or non-oscillating, can, in the present device, rock with its housing on the axis of the hollow projecting portion I 4 to avoid the side friction which would otherwise be caused between the rope or cable and the sides of the groove of the sheave or between the rope or cable and the side plates 8. In other words, the housing and sheave will automaticallyturn on the shaft M to suit the direction of the vertical run 22 of the rope or cable where the load is not directly in the plane which the sheave would assume if it were rigidly or non-revolvably mounted. For this reason the undesirable and excessive friction between the rope or cable and the sheave or the,plates 8 will not develop or occur. This will result in preventing rapid wear of the cable or rope itself, also rapid wear of the flanges 2| at,-the sides of the groove of the sheave, also wear between the rope or cable and the side "plates 8, and in addition, it will avoid the tendency ofthe rope or cable to run off the sheave. Because the oscillating motion of the sheave and housing takes place around the axial line of the projecting portion l4 and because this ,axial line coincides with the axis of the rope or cable in that portion which forms the run 20 the turning or oscillation of the sheave and its housing will not cause a lifting of the lad due to this oscillation of the sheave and its housing, which otherwise would occur except for this position of the axis of rotation of the housing.

The above device is simple and inexpensive and may be used with rigid derricks, such as the types described above; it will avoid excessive wear of the parts and any tendency of the rope or cable to run off the ,sheave.

Having described my invention, what I claim is:

In a tripod derrick, derrick leg connecting and sheave supporting means, comprising a bracket of right angle form, one angle member of which bracket is adapted to be connected endwise to a derrick leg with the other angle member extending perpendicular thereto, and said latter angle member having a bore extended therethrough parallelly of the derrick leg connecting angle member, a stud extended transversely through the angle portion of the bracket adapted for the pivotal connection of derrick legs at opposite sides of the bracket, a bifurcated sheave support the bifurcation legs of which support are of substantially rectangular plate form arranged with alined hubs centrally thereof, and said bifurcated support having a tubular bearing disposed at one side of the axis of the hubs of the bifurcation plates and extending from the support in a direction opposite to the bifurcation legs, said tubular bearing member being extended through and rotatable in the bore of the one angle member of the angle bracket and one end of the bore constricted to guide the run of a cable therethrough, means to retain said tubular bearing member against endwise movement in the bore of the one angle member of the bracket, an axle mounted in the hubs of and extending between the bifurcation plates, and a sheave rotatablysupported on said axle between the bifurcation plates with a peripheral portion of the sheave arranged in a plane coincident with the axis of the bore in the tubular bearing member of the bifurcated support.

JOSEPH W. W-UNSCH. 

